1. To do the job quickly, and cheaply, cutting lots of corners along the way. The finished work appears shabby and unprofessional. Phrase is frequently used by amateurs.

2. An expression of wishful thinking, frequently uttered by inexperienced professionals who think that quality work can be done very quickly and cheaply.

3. An assumption that small-scale projects do not require the same workmanship and attention to detail as larger ones, and therefore can be done successfully without effort.

1.
Amateur producer: You don't need any lights to shoot this scene, right?
Cameraman: Actually I really do, it looks like crap otherwise, way too dark.
Producer: But you can shoot at a high ISO and then brighten the picture in post, right?
Cameraman: Sort of...
Producer: Good. All right guys, let's bang it out!

2.
We're going to bang it out and then take it to fucking Sundance Film Festival.

3.
We'll bang out your little short film while we spend lots of time worrying about our other projects. Your business is valuable to us.